Amorphous alloys which include iron group elements and boron

ABSTRACT

Iron group-boron base amorphous alloys have improved ultimate tensile strength and hardness and do not embrittle when heat treated at temperatures employed in subsequent processing steps, as compared with prior art amorphous alloys. The alloys have the formula 
     
         M.sub.a M&#39;.sub.b Cr.sub.c M&#34;.sub.d B.sub.e 
    
     where M is one iron group element (iron, cobalt or nickel) M&#39; is at least one of the two remaining iron group elements, M&#34; is at least one element of vanadium, manganese, molybdenum, tungsten, niobium and tantalum, &#34;a&#34; ranges from about 40 to 85 atom percent, &#34;b&#34; ranges from 0 to about 45 atom percent, &#34;c&#34; and &#34;d&#34; both range from 0 to about 20 atom percent and &#34;e&#34; ranges from about 15 to 25 atom percent, with the proviso that &#34;b&#34;, &#34;c&#34; and &#34;d&#34; cannot all be zero simultaneously.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention is concerned with amorphous metal alloys and, more particularly, with amorphous metal alloys which include the iron group elements (iron, cobalt and nickel) plus boron.

2. Description of the Prior Art

Novel amorphous metal alloys have been disclosed and claimed by H. S. Chen and D. E. Polk in U.S. Pat. No. 3,856,513, issued Dec. 24, 1974. These amorphous alloys have the formula M_(a) Y_(b) Z_(c), where M is at least one metal selected from the group consisting of iron, nickel, cobalt, chromium and vanadium, Y is at least one element selected from the group consisting of phosphorus, boron and carbon, Z is at least one element selected from the group consisting of aluminum, antimony, beryllium, germanium, indium, tin and silicon, "a" ranges from about 60 to 90 atom percent, "b" ranges from about 10 to 30 atom percent and "c" ranges from about 0.1 to 15 atom percent. These amorphous alloys have been found suitable for a wide variety of applications, including ribbon, sheet, wire, powder, etc. Amorphous alloys are also disclosed and claimed having the formula T_(i) X_(j), where T is at least one transition metal, X is at least one element selected from the group consisting of aluminum, antimony, beryllium, boron, germanium, carbon, indium, phosphorus, silicon and tin, "i" ranges from about 70 to 87 atom percent and "j" ranges from about 13 to 30 atom percent. These amorphous alloys have been found suitable for wire applications.

At the time these amorphous alloys were discovered, they evidenced mechanical properties that were superior to then-known polycrystalline alloys. Such superior mechanical properties included ultimate tensile strengths up to 350,000 psi, hardness values of about 600 to 750 DPH and good ductility. Nevertheless, new applications requiring improved magnetic, physical and mechanical properties and higher thermal stability have necessitated efforts to develop further specific compositions.

SUMMARY OF THE INVENTION

In accordance with the invention, iron group-boron base amorphous alloys have improved ultimate tensile strength and hardness and do not embrittle when heat treated at temperatures employed in subsequent processing steps. These amorphous metal alloys also have desirable magnetic properties. These amorphous alloys consist essentially of the composition

    M.sub.a M'.sub.b Cr.sub.c M".sub.d B.sub.e

where M is one element selected from the group consisting of iron, cobalt and nickel, M' is one or two elements selected from the group consisting of iron, cobalt and nickel other than M, M" is at least one element of vanadium, manganese, molybdenum, tungsten, niobium and tantalum, "a" ranges from about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent "c" and "d" each ranges from 0 to about 20 atom percent and "e" ranges from about 15 to 25 atom percent, with the proviso that "b", "c" and "d" cannot all be zero simultaneously.

Preferably, chromium is present in an amount of about 4 to 16 atom percent of the total alloy composition to attain enhanced mechanical properties, improved thermal stability, and corrosion and oxidation resistance. Preferred compositions also include compositions where M" is molybdenum, present in an amount of about 0.4 to 8 atom percent of the total alloy composition to attain increased hardness. For preferred compositions having desirable magnetic properties, "c" and "d" are both zero.

The alloys of this invention are at least 50% amorphous, and preferably at least 80% amorphous and most preferably about 100% amorphous, as determined by X-ray diffraction.

The amorphous alloys in accordance with the invention are fabricated by a processs which comprises forming melt of the desired composition and quenching at a rate of about 10⁵ ° to 10⁶ ° C/sec by casting molten alloy onto a chill wheel or into a quench fluid. Improved physical and mechanical properties, together with a greater degree of amorphousness, are achieved by casting the molten alloy onto a chill wheel in a partial vacuum having an absolute pressure of less than about 5.5 cm of Hg.

DETAILED DESCRIPTION OF THE INVENTION

There are many applications which require that an alloy have, inter alia, a high ultimate tensile strength, high thermal stability and ease of fabricability. For example, metal ribbons used in razor blade applications usually undergo a heat treatment of about 370° C for about 30 min to bond an applied coating of polytetrafluoroethylene to the metal. Likewise, metal strands used as tire cord undergo a heat treatment of about 160° to 170° C for about 1 hr to bond tire rubber to the metal.

When crystalline alloys are employed, phase changes can occur during heat treatment that tend to degrade the physical and mechanical properties. Likewise, when amorphous alloys are employed, a complete or partial transformation from the glassy state to an equilibrium or a metastable crystalline state can occur during heat treatment. As with inorganic oxide glasses, such a transformation degrades physical and mechanical properties such as ductility, tensile strength, etc.

The thermal stability of an amorphous metal alloy is an important property in certain applications. Thermal stability is characterized by the time-temperature transformation behavior of an alloy, and may be determined in part by DTA (differential thermal analysis). As considered here, relative thermal stability is also indicated by the retention of ductility in bending after thermal treatment. Alloys with similar crystallization behavior as observed by DTA may exhibit different embrittlement behavior upon exposure to the same heat treatment cycle. By DTA measurement, crystallization temperatures, T_(c), can be accurately determined by slowly heating an amorphous alloy (at about 20° to 50° C/min) and noting wheter excess heat is evolved over a limited temperature range (crystallization temperature) or whether excess heat is absorbed over a particular temperature range (glass transition temperature). In general, the glass transition temperature T_(g) is near the lowest, or first, crystallization temperature, T_(cl), and, as is convention, is the temperature at which the viscosity ranges from about 10¹³ to 10¹⁴ poise.

Most amorphous metal alloy compositions containing iron, nickel, cobalt and chromium which include phosphorus, among other metalloids, evidence ultimate tensile strengths of about 265,000 to 350,000 psi and crystallization temperatures of about 400° to 460° C. For example, an amorphous alloy have the composition Fe₇₆ P₁₆ C₄ Si₂ Al₂ (the subscripts are in atom percent) has an ultimate tensile strength of about 310,000 psi and a crystallization temperature of about 460° C, an amorphous alloy having the composition Fe₃₀ Ni₃₀ Co₂₀ P₁₃ B₅ Si₂ has an ultimate tensile strength of about 265,000 psi and a crystallization temperature of about 415° C, and an amorphous alloy having the composition Fe₇₄.3 Cr₄.5 P₁₅.9 C₅ B₀.3 has an ultimate tensile strength of about 350,000 psi and a crystallization temperature of 446° C. The thermal stability of these compositions in the temperature range of about 200° to 350° C is low, as shown by a tendency to embrittle after heat treating, for example, at 250° C for 1 hr or 300° C for 30 min or 330° C for 5 min. Such heat treatments are required in certain specific applications, such as curing a coating of polytetrafluoroethylene on razor blade edges or bonding tire rubber to metal wire strands.

In accordance with the invention, iron group-boron base amorphous alloys have improved ultimate tensile strength and a hardness and do not embrittle when heat treated at temperatures typically employed in subsequent processing steps. These amorphous metal alloys consist essentially of the composition

    M.sub.a M'.sub.b Cr.sub.c M".sub.d B.sub.e

where M is one iron group element (iron, cobalt or nickel), M' is at least one of the remaining two iron group elements, M" is at least one element of vanadium, manganese, molybdenum, tungsten, niobium and tantalum, "a" ranges from about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent "c" and "d" each ranges from 0 to about 20 atom percent and "e" ranges from about 15 to 25 atom percent, with the proviso that "b", "c" and "d" cannot all be zero simultaneously. Examples of amorphous alloy compositions in accordance with the invention include Fe₅₀ Ni₅ Co₇ Cr₁₀ Mo₁₀ B₁₈, Fe₄₀ Ni₂₀ Co₁₀ Cr₁₀ B₂₀, Ni₄₆ Fe₁₃ Co₁₃ Cr₉ Mo₃ B₁₆, Co₅₀ Fe₁₈ Ni₁₅ B₁₇, Fe₆₅ V₁₅ B₂₀ and Ni₅₈ Mn₂₀ B₂₂. The purity of all compositions is that found in normal commercial practice.

The amorphous metal alloys in accordance with the invention typically evidence ultimate tensile strengths ranging from about 370,000 to 520,000 psi, hardness values ranging from about 925 to 1190 DPH and crystallization temperatures ranging from about 370° to 610° C.

Optimum resistance to corrosion and oxidation is obtained by including about 4 to 16 atom percent of chromium in the alloy composition. Addition of such amounts of chromium in general also enhances the crystallization temperature, the tensile strength, and the thermal stability of the amorphous metal alloys. Below about 4 atom percent, insufficient corrosion inhibiting behavior is observed, while greater than about 16 atom percent of chromium tends to decrease the resistance to embrittlement upon heat treatment at elevated temperatures of the amorphous metal alloys.

An increase in hardness and crystallization temperature is achieved where M" is molybdenum. Preferably, about 0.4 to 8 atom percent of molybdenum is included in the alloy composition. Below about 0.4 atom percent, a substantial increase in hardness is not obtained. Above about 8 percent, while increased hardness values are obtained, the thermal stability is reduced, necessitating a balancing of desired properties. For many compositions, improved mechanical properties and increased crystallization temperatures are achieved, at some sacrifice in thermal stability, by including about 4 to 8 atom percent of molybdenum in the entire alloy composition. For example, an amorphous metal alloy having the composition Fe₆₇ Ni₅ Co₃ Cr₇ B₁₈ has a crystallization temperature of 488° C, a hardness of 1003 DPH and an ultimate tensile strength of 417,000 psi, while an amorphous metal alloy having the composition Fe₆₃ Ni₅ Co₃ Cr₇ Mo₄ B₁₈ has a crystallization temperature of 528° C, a hardness of 1048 DPH and an ultimate tensile strength of 499,000 psi. For some compositions, improved thermal stability and improved hardness is unexpectedly achieved by including about 0.4 to 0.8 atom percent of molybdenum in the allow composition. For comparison, an amorphous metal alloy having the composition Fe₆₆ Ni₅ Co₄ Cr₈ B₁₇ has a hardness of 1038 DPH and remains ductile after heat treatment at 360° C for 30 min, but embrittles after heat treatment at 370° for 30 min; an amphorous metal alloy having the composition Fe₆₆ Ni₅ Co₃.2 Cr₈ Mo₀.8 B₁₇ has a hardness of 1108 DPH and remains ductile after heat treatment at 370° C for 30 min.

Many preferred compositions ranges within he inventive compositions range may be set forth, depending upon specific desired improved properties.

For iron base amorphous metal alloys, high strength and high hardness are obtained for alloys having compositions in the range

    Fe.sub.50-70 (Ni,Co).sub.5-15 Cr.sub.5-16 Mo.sub.0-8 B.sub.16-22.

examples include Fe₅₄ Ni₆ Co₅ Cr₁₆ Mo₂ B₁₇, Fe₆₀ Ni₇ Co₇ Cr₈ B₁₈ and Fe₆₃ Ni₅ Co₃ Cr₇ Mo₄ B₁₈. The ultimate tensile strength of such compositions typically range from about 415,000 to 500,000 psi, the hardness values range from about 1025 to 1120 DPH, and the crystallization temperatures range from about 480° to 550° C. Alloys within this composition range have been found particularly suitable for fabricating tire cord filaments.

High thermal stability is obtained for alloys having compositions in the range

    Fe.sub.60-67 Ni.sub.3-7 Co.sub.3-7 Cr.sub.7-10 Mo.sub.0.4-0.8 B.sub.17.

examples include Fe₆₆ Ni₅ Co₃.6 Cr₈ Mo₀.4 B₁₇ and Fe₆₆ Ni₅ Co₃.2 Cr₈ Mo₀.8 B₁₇. Such compositions generally remain ductile to bending following heat treatments at 360° to 370° C for 1/2 hr. Alloys within this composition range have been found particularly suitable for fabricating razor blade strips.

For nickel base amorphous metal alloys, high hardness, moderately high strength, high thermal stability and corrosion resistance are obtained for alloys having composition in the range

    Ni.sub.40-50 Fe.sub.4-15 Co.sub.5-25 Cr.sub.8-12 Mo.sub.0-9 B.sub.15-22.

examples in include Ni₄₀ Fe₅ Co₂₀ Cr₁₀ Mo₉ Br₁₆, Ni₄₅ Fe₅ Co₂₀ Cr₁₀ Mo₉ B₁₆ Ni₄₅ Fe₅ Co₂₀ Cr₁₀ Mo₄ B₁₆ and Ni₅₀ Fe₅ Co₁₇ Cr₉ Mo₃ B₁₆. The ultimate strengths of such compositions are typically about 395,000 to 415,000 psi; the hardness values typically range from about 980 to 1045 DPH.

For cobalt base amorphous metal alloys, high strength, high thermal stability and high hardness are obtained for alloys having compositions in the range

    Co.sub.40-50 Fe.sub.5-20 Ni.sub.0-20 Cr.sub.4-15 Mo.sub.0-9 B.sub.15-23.

examples include Co₄₅ Fe₁₇ Ni₁₃ Cr₅ Mo₃ B₁₇, Co₅₀ Fe₁₅ Cr₁₅ Mo₄ B₁₆, Co₄₆ Fe₁₈ Ni₁₅ Mo₄ B₁₇ and Co₅₀ Fe₁₀ Ni₁₀ Cr₁₀ B₂₀. The hardness values of such compositions are typically about 1100 DPH.

Preferred amorphous metal alloys having desirable magnetic properties depend on the specific application desired. For such compositions, both "c" and "d" are zero. For high saturation magnetization values, e.g., about 13 to 17 kGauss, it is desired that a relatively high amount of cobalt and/or iron be present. Examples include Fe₈₁ Co₃ Ni₁ B₁₅ and Fe₈₀ Co₅ B₁₅. For low coercive force less than about 0.5 Oe, it is desired that a relatively high amount of nickel and/or iron be present. Examples include Ni₅₀ Fe₃₂ B₁₈ and Fe₅₀ Ni₂₀ Co₁₅ B₁₅. Suitable magnetic amorphous metal alloys have compositions in the range

    Fe.sub.40-80 Co.sub.5-45 B.sub.15≅

    co.sub.40-80 Fe.sub.5-45 B.sub.15-25

    fe.sub.40-80 Ni.sub.5-45 B.sub.15-25

ti Ni₄₀₋₈₀ Fe₅₋₄₅ B₁₅₋₂₅

    co.sub.40-80 Ni.sub.5-45 B.sub.15-25

    ni.sub.40-65 Co.sub.20-45 B.sub.15-25

    fe.sub.40-70 Ni.sub.4-25 Co.sub.5-30 B.sub.15-25

    ni.sub.40-70 Fe.sub.5-25 Co.sub.5-25 B.sub.15-25

    co.sub.40-70 Fe.sub.5-25 Ni.sub.5-25 B.sub.15-25.

examples include Fe₆₀ Co₂₀ B₂₀, Co₇₀ Fe₁₀ B₂₀, Co₄₀ Fe₄₀ B₂₀, Ni₇₀ Fe₁₂ B₁₈, Fe₅₂ Ni₃₀ B₁₈, Fe₆₂ Ni₂₀ B₁₈, Co₇₂ Ni₁₀ B₁₈, Co₆₂ Ni₂₀ B₁₈, Fe₇₀ Ni₇.5 Co₇.5 B₁₅, Fe₅₀ Ni₅ Co₂₈ B₁₇, Fe₅₀ Ni₂₀ Co₁₅ B₁₅, Fe₆₀ Ni₇ Co₁₂ B₂₁, Fe₇₀ Ni₄ Co₅ B₂₁, Ni₅₀ Fe₁₈ Co₁₅ B₁₇, co₅₀ Fe₁₈ Ni₁₅ B₁₇ and Co₆₀ Fe₁₃ Ni₁₀ B₁₇.

The amorphous alloys are formed by cooling a melt at a rate of about 10⁵⁰ to 10⁶ °C/sec. A variety of techniques are available, as is now well-known in the art, for fabrication splat-quenched foils and rapid-quenched continuous ribbons, wire, sheet, etc. Typically, a particular composition is selected, powders of the requisite elements (or of materials that decompose to form the elements, such as ferroboron, ferrochrome, etc.) in the desired proportions are melted and homogenized, and the molten alloy is rapidly quenched either on a chill surface, such as a rotating cooled cylinder, or in a suitable fluid medium, such as a chilled brine solution. The amorphous alloys may be formed in air. However, superior mechanical properties are achieved by forming these amorphous alloys in a partial vacuum with absolute pressure less than about 5.5 cm of Hg, and preferably about 100μ m to 1 cm of Hg, as disclosed in a patent application of R. Ray et al., Ser. No. 552,673, filed Feb. 24, 1975.

The amorphous metal alloys are at least 50% amorphous, and preferably at least 80% amorphous, as measured by X-ray diffraction. However, a substantial degree of amorphousness approaching 100% amorphous is obtained by forming these amorphous metal alloys in a partial vacuum. Ductility is thereby improved, and such alloys possessing a substantial degree of amorphousness are accordingly preferred.

The amorphous metal alloys of the present invention evidence superior fabricability, compared with prior art compositions. In addition to their improved resistance to embrittlement after heat treatment, these compositions tend to be more oxidation and corrosion resistant than prior art compositions.

These compositions remain amorphous at heat treating conditions under which phosphorus-containing amorphous alloys tend to embrittle. Ribbons of these alloys find use in applications requiring relatively high thermal stability and increased mechanical strength.

EXAMPLES

Rapid melting and fabrication of amorphous strips of ribbons of uniform width and thickness from high melting (about 1100° to 1600° C) reactive alloys was accomplished under vacuum. The application of vacuum minimized oxidation and contamination of the alloy during melting or squirting and also eliminated surface damage (blisters, bubbles, etc.) commonly observed in strips processed in air or inert gas at 1 atm. A copper cylinder was mounted vertically on the shaft of a vacuum rotary feedthrough and placed in a stainless steel vacuum chamber. The vacuum chamber was a cylinder flanged at two ends wth two side ports and was connected to a diffusion pumping system. The copper cylinder was rotated by variable speed electric motor via the feedthrough. A crucible surrounded by an induction coil assembly was located above the rotating cylinder inside the chamber. An induction power supply was used to melt alloys contained in crucibles made of fused quartz, boron nitride, alumina, zirconia or beryllia. The amorphous ribbons were prepared by melting the alloy in a suitable non-reacting crucible and ejecting the melt by over-pressure of argon through an orifice in the bottom of the crucible onto the surface of the rotating (about 1500 to 2000 rpm) cylinder. The melting and squirting were carried out in a partial vacuum of about 100 μ m, usng an inert gas such as argon to adjust the vacuum pressure.

Using the vacuum-melt casting apparatus described above, a number of various glass-forming iron group-boron base alloys were chill cast as continuous ribbons having substantially uniform thickness and width. Typically, the thickness ranged from 0.001 to 0.003 inch and the width ranged from 0.05 to 0.12 inch. The ribbons were checked for amorphousness by X-ray diffraction and DTA. Hardness (in DPH) was measured by the diamond pyramid technique, using a Vickers-type indenter consisting of a diamond in the form of a square-based pyramid with an included angle of 136° between opposite faces. Tensile tests to determine ultimate tensile strength (in psi) were carried out using an Instron machine. The mechanical behavior of amorphous metal alloys having compositions in accordance with the invention was measured as a function of heat treatment. All alloys were fabricated by the process given above. The amorphous ribbons of the alloys were all ductile in the as-quenched condition. The ribbons were bent end on end to form a loop. The diameter of the loop was gradually reduced between the anvils of a micrometer. The ribbons were considered ductile if they could be bent to a radius of curvature less than about 0.005 inch without fracture. If a ribbon fractured, it was considered to be brittle.

EXAMPLE 1 Alloys Suitable for Tire Cord Applications

Alloys that would be suitable for tire cord applications, such as for metal belts in radial-ply tires, must be able to withstand about 160° to 170° C for about 1 hr, which is the temperature usually employed in curing a rubber tire. The alloys must also be resistant to corrosion by sulfur and evidence high mechanical strength. Examples of compositions of alloys suitable for tire cord applications and their crystallization temperature in ° C are listed in Table I below. These alloys are described by the composition Fe₅₀₋₇₀ (Ni,Co)₅₋₁₅ Cr₅₋₁₆ Mo₀₋₈ B₁₆₋₂₂.

The alloys were prepared under the conditions described above. All alloys remained ductile and fully amorphous following heat treatment at 200° C for 1 hr. After the foregoing heat treatment, these alloys retained the hardness and mechanical strength values observed for the as-quenched alloys.

                  TABLE I                                                          ______________________________________                                         Thermal and Mechanical Properties of Some Iron-Group-Boron                     Base Amorphous Compositions Suitable for Tire Cord                             Applications                                                                                                       Ultimate                                                           Crystallization                                                                            Tensile                                    Alloy Composition                                                                             Hardness Temperature Strength                                   (Atom Percent) (DPH)    (° C)                                                                               (psi)                                      ______________________________________                                         Fe.sub.67 Ni.sub.5 Co.sub.3 Cr.sub.7 B.sub.18                                                 1083     488         417,000                                    Fe.sub.63 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.4 B.sub.18                                        1048     528         499,000                                    Fe.sub.60 Ni.sub.7 Co.sub.7 Cr.sub.8 B.sub.18                                                 1025     481         488,000                                    Fe.sub.59 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.8 B.sub.18                                        1120     553,624     413,000                                    Fe.sub.55 Ni.sub.10 Co.sub.5 Cr.sub.10 B.sub.20                                               1048     487         477,000                                    Fe.sub.55 Ni.sub.8 Co.sub.5 Cr.sub.15 B.sub.17                                                1085     496         455,000                                    Fe.sub.54 Ni.sub.6 Co.sub.5 Cr.sub.16 Mo.sub.2 B.sub.17                                       1097     519         478,000                                    Fe.sub.53 Ni.sub.6 Co.sub.5 Cr.sub.16 Mo.sub.3 B.sub.17                                       1033     508         444,000                                    ______________________________________                                    

EXAMPLE 2 Alloys Suitable for Razor Blade Applications

Alloys that would be suitable for razor blade applications must be able to withstand about 370° C for about 30 min, which is the processing condition required to apply a coating of polytetrafluoroethylene to the cutting edge. Such alloys should be able to remain ductile and fully amorphous and retain high hardness and corrosion resistance behavior after the foregoing heat treatment. Table II below lists some typical compositions of the suitable for use as razor blades. These alloys are described by the composition Fe₆₀₋₆₇ Ni₃₋₇ Co₃₋₇ Cr₇₋₁₀ Mo₀.4-0.8 B₁₇.

All alloys remain ductile and fully amorphous after heat treatment of 370° C for 30 min. After the foregoing heat treatment, these alloys retained the hardness and corrosion resistant behavior observed for the as-quenched alloys.

                  TABLE II                                                         ______________________________________                                         Thermal and Mechanical Properties of Some Iron Group-Boron                     Base Amorphous Compositions Suitable                                           for Razor Blade Applications                                                                    Hardness  Crystallization                                     Composition (atom percent)                                                                      (DPH)     Temperature, ° C                             ______________________________________                                         Fe.sub.66 Ni.sub.5 Co.sub.3.6 Cr.sub.8 Mo.sub.0.4 B.sub.17                                      1108      487                                                 Fe.sub.66 Ni.sub.5 Co.sub.3.4 Cr.sub.8 Mo.sub.0.6 B.sub.17                                      1101      494                                                 Fe.sub.66 Ni.sub.5 Co.sub.3.2 Cr.sub.8 Mo.sub.0.8 B.sub.17                                      1105      498                                                 ______________________________________                                    

EXAMPLE 3 Alloys Having High Strength and High Hardness Values Other alloys having high hardness and high crystallization temperature values are given in Table III. These alloys are described by the general composition M₄₀₋₈₅ M'₀₋₄₅ Cr₀₋₂₀ Mo₀₋₂₀ B₁₅₋₂₅ Such alloys are useful in, for example, structural applications.

                  TABLE III                                                        ______________________________________                                         Thermal and Mechanical Properties of Some Iron Group-                          Boron Base Amorphous Alloys                                                    Alloy Composition                                                                               Hardness  Crystallization                                     (Atom Percent)   (DPH)     Temperature (° C)                            ______________________________________                                         Fe.sub.72 Ni.sub.4 Co.sub.3 Cr.sub.5 B.sub.16                                                   1086      440,492                                             Fe.sub.66 Ni.sub.5 Co.sub.4 Cr.sub.8 B.sub.17                                                   1088      486                                                 Fe.sub.65 Ni.sub.5 Co.sub.3 Cr.sub.10 B.sub.17                                                  1096      478                                                 Fe.sub.65 Ni.sub.2 Co.sub.2 Cr.sub.4 Mo.sub.10 B.sub.17                                         1130      547                                                 Fe.sub.65 V.sub.15 B.sub.20                                                                               485                                                 Fe.sub.63 Co.sub.10 Cr.sub.7 Mo.sub.2 B.sub.18                                                  1130      512                                                 Fe.sub.62 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.5 B.sub.18                                          1115      530                                                 Fe.sub.60 Ni.sub.5 Co.sub.10 Cr.sub.5 B.sub.20                                                  1085      475                                                 Fe.sub.60 Ni.sub.5 Co.sub.3 Cr.sub.5 Mo.sub.10 B.sub.17                                         1120      518                                                 Fe.sub.60 Co.sub.10 Cr.sub.10 B.sub.20                                                          1099      495                                                 Fe.sub.58 Mn.sub.22 B.sub.20                                                                              483                                                 Fe.sub.55 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.12 B.sub.18                                         1136      581                                                 Fe.sub.50 Ni.sub.10 Co.sub.10 Cr.sub.10 B.sub.20                                                1020      483                                                 Fe.sub.50 Co.sub.15 Cr.sub.15 Mo.sub.4 B.sub.16                                                 1128      529,588                                             Fe.sub.45 Ni.sub.15 Co.sub.10 Cr.sub.10 B.sub.20                                                1017      484                                                 Fe.sub.40 Ni.sub.20 Co.sub.10 Cr.sub.10 B.sub.20                                                 990      481                                                 Fe.sub.40 Ni.sub.8 Co.sub.5 Cr.sub.10 Mo.sub.20 B.sub.17                                        1187      607,677                                             Ni.sub.65 V.sub.15 B.sub.20                                                                               505                                                 Ni.sub.58 Mn.sub.20 B.sub.22                                                                              517                                                 Co.sub.45 Fe.sub.17 Ni.sub.13 Cr.sub.5 Mo.sub.3 B.sub.17                                        1108      540,628                                             ______________________________________                                    

EXAMPLE 4 Nickel Base Amorphous Metal Alloys

Table IV lists the composition, hardness and crystallization temperature of some nickel base amorphous alloys containing boron. These alloys were also found to possess high mechanical strength. The alloys are described by the composition Ni₄₀₋₅₀ Fe₄₋₁₅ Co₅₋₂₅ Cr₈₋₁₂ Mo₀₋₉ B₁₅₋₂₃.

                  TABLE IV                                                         ______________________________________                                         Thermal and Mechanical Properties of Some Nickel Base                          Amorphous Alloys with Boron                                                                            Ultimate                                                                       Tensile  Crystallization                               Alloy Composition                                                                             Hardness Strength Temperature                                   (Atom percent) (DPH)    (psi)    (° C)                                  ______________________________________                                         Ni.sub.50 Fe.sub.5 Co.sub.17 Cr.sub.9 Mo.sub.3 B.sub.16                                       977               432                                           Ni.sub.47 Fe.sub.4 Co.sub.23 Cr.sub.9 Mo.sub.1 B.sub.16                                       982               400,473,575                                   Ni.sub.46 Fe.sub.4 Co.sub.23 Cr.sub.9 Mo.sub.2 B.sub.16                                       981               420,500                                       Ni.sub.46 Fe.sub.10 Co.sub.20 Cr.sub.8 B.sub.16                                               980               400,470,580                                   Ni.sub.46 Fe.sub.13 Co.sub.13 Cr.sub.9 Mo.sub.3 B.sub.16                                      995               439,542                                       Ni.sub.45 Fe.sub.5 Co.sub.20 Cr.sub.10 Mo.sub.4 B.sub.16                                      1033     396,000  463,560                                       Ni.sub.44 Fe.sub.20 Co.sub.5 Cr.sub.10 Mo.sub.4 B.sub.17                                      1024              422,608                                       Ni.sub.44 Fe.sub.5 Co.sub.24 Cr.sub.10 B.sub.17                                               1001              425,463,615                                   Ni.sub.40 Fe.sub.6 Co.sub.20 Cr.sub.12 Mo.sub.6 B.sub.16                                      1033     396,000  478,641                                       Ni.sub.40 Fe.sub.5 Co.sub.20 Cr.sub.10 Mo.sub.9 B.sub.16                                      1043     413,000  466,570,673                                   ______________________________________                                         cl EXAMPLE 5

Magnetic Alloys

The thermal properties of compositions found to be useful in magnetic applications are given in Table V. For some alloys, the room temperature saturation magnetization (M_(s)) in kGauss or the coercive force (H_(c)) in Oe of a strip under DC conditions is listed.

EXAMPLE 6 Corrosion-resistant Alloys

A number of iron group-boron base amorphous metal alloys were kept immersed in a solution of 10 wt% NaCl in water at room temperature for 450 hrs and subsequently visually inspected for their corrosion or oxidation characteristics. The results are given in Table VI. The amorphous alloys containing chromium showed excellent resistance to any corrosion or oxidation.

                  TABLE V                                                          ______________________________________                                         Thermal Properties of Some Magnetic Alloys                                                                   Crystal-                                                        Saturation     lization                                         Alloy Composition                                                                             Magnetization (M.sub.s) or                                                                    Temperature                                      (Atom percent) Coercive Force (H.sub.c)                                                                      (° C)                                     ______________________________________                                         Fe.sub.40-80 Co.sub.5-45 B.sub.15-25 :                                         Fe.sub.80 Co.sub.5 B.sub.15                                                                   M.sub.s =15.6 kGauss                                                                          --                                               Fe.sub.70 Co.sub.10 B.sub.20  465                                              Fe.sub.50 Co.sub.30 B.sub.20  493                                              Fe.sub.40 Co.sub.40 B.sub.20  492                                              Co.sub.40-80 Fe.sub.5-45 B.sub.15-25 :                                         Co.sub.60 Fe.sub.20 B.sub.20  483                                              Ni.sub.40-80 Fe.sub.5-45 B.sub.15-25 :                                         Ni.sub.70 Fe.sub.12 B.sub.18  435                                              Ni.sub.60 Fe.sub.22 B.sub.18                                                                  H.sub.c =0.059 Oe                                                                             444                                              Ni.sub.50 Fe.sub.32 B.sub.18                                                                  H.sub.c =0.029 Oe                                                                             456                                              Fe.sub.40-70 Ni.sub.4-25 Co.sub.5-30 B.sub.15-25 :                             Fe.sub.70 Ni.sub.4 Co.sub.5 B.sub.21                                                                         455                                              Fe.sub.70 Ni.sub.7.5 Co.sub.7.5 B.sub.15                                                      M.sub.s =13.7 kGauss                                                                          435,504                                          Fe.sub.65 Ni.sub.7 Co.sub.7 B.sub.21                                                          M.sub.s =13.45 kGauss                                                                         465                                              Fe.sub.60 Ni.sub.7 Co.sub.12 B.sub.21                                                                        472                                              Fe.sub.50 Ni.sub.20 Co.sub.15 B.sub.15                                                        H.sub.c =0.038 Oe                                                                             422,458                                          Fe.sub.50 Ni.sub.5 Co.sub.28 B.sub.17                                                                        450,492                                          Fe.sub.40 Ni.sub.15 Co.sub.25 B.sub.20                                                                       473                                              Ni.sub.40-70 Fe.sub.5-25 Co.sub.5-25 B.sub.15-25 :                             Ni.sub.60 Fe.sub.13 Co.sub.10 B.sub.17                                                                       373                                              Ni.sub.50 Fe.sub.18 Co.sub.15 B.sub.17                                                                       405                                              Ni.sub.40 Fe.sub.20 Co.sub.23 B.sub.17                                                                       423                                              Co.sub.40-70 Fe.sub.5-25 Ni.sub.5-25 B.sub.15-25 :                             Co.sub.68 Fe.sub.7.5 Ni.sub.7.5 B.sub.17                                                                     432                                              Co.sub.60 Fe.sub.13 Ni.sub.10 B.sub.17                                                                       442                                              Co.sub.50 Fe.sub.18 Ni.sub.15 B.sub.17                                                                       437,450                                          Co.sub.40 Fe.sub.20 Ni.sub.17 B.sub.23                                                                       462                                              Other:                                                                         Fe.sub.81 Co.sub.3 Ni.sub.1 B.sub.15                                                          M.sub.s =15.1 kGauss                                                                          --                                               ______________________________________                                    

                  TABLE VI                                                         ______________________________________                                         Results of Corrosion Test of Some Iron, Nickel and Cobalt                      Base Amorphous Alloys with Boron                                               Fe.sub.66 Ni.sub.5 Co.sub.3.6 Cr.sub.8 Mo.sub.0.4 B.sub.17                                      No corrosion, oxidation                                                         or discoloration                                             Fe.sub.65 Ni.sub.5 Co.sub.3 Cr.sub.10 B.sub.17                                                  "                                                             Fe.sub.63 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.4 B.sub.18                                          "                                                             Fe.sub.55 Ni.sub.8 Co.sub.5 Cr.sub.15 B.sub.17                                                  "                                                             Fe.sub.54 Ni.sub.6 Co.sub.5 Cr.sub.15 Mo.sub.2 B.sub.18                                         "                                                             Fe.sub.50 Ni.sub.10 Co.sub.10 Cr.sub.10 B.sub.20                                                "                                                             Fe.sub.40 Ni.sub.15 Co.sub.25 B.sub.20                                                          Corroded & tarnished                                          Ni.sub.44 Fe.sub.20 Co.sub.5 Cr.sub.10 Mo.sub.4 B.sub.17                                        No corrosion, oxidation                                                         or discoloration                                             Ni.sub.40 Fe.sub.5 Co.sub.20 Cr.sub.10 Mo.sub.9 B.sub.16                                        "                                                             Co.sub.50 Fe.sub.18 Ni.sub.15 B.sub.17                                                          Corroded & tarnished                                          ______________________________________                                    

EXAMPLE 7 Thermal Aging of Alloys

A number of iron group-boron base amorphous metal alloys were thermally aged in the temperature range 250° to 375° C in air for 1/2 to 1 hr and evaluated for embrittlement. The heat treated strips were bent to form a loop. The diameter of the loop was gradually reduced between the anvils of a micrometer until fracture occurred. The average breaking diameter of the amorphous alloy strip obtained from micrometer readings is indicative of its ductility. A low number indicates good ductility. For example, the number zero means that the amorphous ribbon is fully ductile. The results are tabulated in Tables VII and VIII.

    __________________________________________________________________________                   Average Breaking Diameter (mis)                                  Alloy Composition                                                                            Thickness                                                                            250° C                                                                      275° C                                                                      300° C                                                                      325° C                                                                      345° C                                                                      360° C                                                                      375° C                                                                      Crystallization                (Atom Percent)                                                                               (mils)                                                                               1 hr                                                                               1 hr                                                                               1 hr                                                                               1 hr                                                                               1/2 hr                                                                             1/2 hr                                                                             1/2 hr                                                                             Temperature (°          __________________________________________________________________________                                                     C)                             Fe.sub.66 Ni.sub.5 Co.sub.3.2 Cr.sub.8 Mo.sub.0.8 B.sub.17                                   2     0   0   0   0   0   0   0   498                            Fe.sub.66 Ni.sub.5 Co.sub.3.6 Cr.sub.8 Mo.sub.0.4 B.sub.17                                   1.35  0   0   0   0   0   0   0   487                            Fe.sub.66 Ni.sub.5 Co.sub.3.8 Cr.sub.8 Mo.sub.0.2 B.sub.17                                   1.4   0   0   0   0   0   0   10  488                            Fe.sub.66 Ni.sub.5 Co.sub.4 Cr.sub.8 B.sub.17                                                1.2   0   0   0   0   0   0   30  486                            Fe.sub.67 Ni.sub.5 Co.sub.3 Cr.sub.7 B.sub.18                                                1.8   0   0   0   0   0   0   30  488                            Fe.sub.65 Ni.sub.5 Co.sub.3 Cr.sub.10 B.sub.17                                               1.7   0   0   0   0   0   0   37  478                            Fe.sub.60 Ni.sub.7 Co.sub.7 Cr.sub.8 B.sub.18                                                1.5   0   0   0   0   0   25      481                            Fe.sub.63 Ni.sub.5 Co.sub.3 Cr.sub.7 Mo.sub.4 B.sub.18                                       2.3   0   0   0   40  50          528                            Fe.sub.45 Ni.sub.15 Co.sub.10 Cr.sub.10 B.sub.20                                             1.45  0   0   0   35              484                            Fe.sub.55 Ni.sub.10 Co.sub.5 Cr.sub.10 B.sub.20                                              1.8   0   0   0   50              487                            Fe.sub.55 Ni.sub.8 Co.sub.5 Cr.sub.15 B.sub.17                                               1.75  0   0   16  35  45          496                            Fe.sub.65 Ni.sub.2 Co.sub.2 Cr.sub.4 Mo.sub.10 B.sub.17                                      1.6   0   0   25                  547                            Fe.sub.65 Ni.sub.7 Co.sub.7 B.sub.21                                                         1.5   0   0   25                  465                            Fe.sub.70 Ni.sub.4 Co.sub.5 B.sub.21                                                         1.6   0   0   30                  455                            Fe.sub.54 Ni.sub.6 Co.sub.5 Cr.sub.16 Mo.sub.2 B.sub.17                                      2     0   0   30                  519                            Fe.sub.53 Ni.sub.6 Co.sub.5 Cr.sub.16 Mo.sub.3 B.sub.17                                      1.7   0   35                      508                            __________________________________________________________________________

                                      TABLE VIII                                   __________________________________________________________________________     Results of Embrittlement Studies on Nickel-Base Boron                          Amorphous Metal Alloys                                                                            Average Breaking Diameter (mils)                            Alloy Composition                                                                           Thickness                                                                            325° C                                                                      340° C                                                                      355° C                                                                      360° C                                                                      375° C                               (Atom percent)                                                                              (mils)                                                                               1/2 hr                                                                             1/2 hr                                                                             1/2 hr                                                                             1/2 hr                                                                             1/2 hr                                      __________________________________________________________________________     Ni.sub.45 Fe.sub.5 Co.sub.20 Cr.sub.10 Mo.sub.4 B.sub.16                                    1.5   0   0   0   0   0                                           Ni.sub.44 Fe.sub.5 Co.sub.24 Cr.sub. 10 B.sub.17                                            1.35  0   0   0   0   15                                          Ni.sub.50 Fe.sub.5 Co.sub.17 Cr.sub.9 Mo.sub.3 B.sub.16                                     1.2   0   0   0   20                                              Ni.sub.46 Fe.sub.4 Co.sub.23 Cr.sub.9 Mo.sub.2 B.sub.16                                     1.4   0   0   0   25                                              Ni.sub.46 Fe.sub.10 Co.sub. 20 Cr.sub.8 B.sub.16                                            1.2   0   0   15                                                  Ni.sub.46 Fe.sub.13 Co.sub.13 Cr.sub.9 Mo.sub.3 B.sub.16                                    1.4   0   10                                                      Ni.sub.40 Fe.sub.6 Co.sub.20 Cr.sub.12 Mo.sub.6 B.sub.16                                    1.4   0   15                                                      Ni.sub.40 Fe.sub.5 Co.sub.20 Cr.sub.10 Mo.sub.9 B.sub.16                                    1.4   0   25                                                      __________________________________________________________________________ 

What is claimed is:
 1. An amorphous metal alloy that is at least 50% amorphous, has improved ultimate tensile strength and hardness and does not embrittle when heat treated, characterized in that the alloy consists essentially of the composition M_(a) M'_(b) Cr_(c) M"_(d) B_(e), where M is one element selected from the group consisting of iron, cobalt and nickel, M' is one or two elements selected from the group consisting of iron, cobalt and nickel other than M, M" is at least one element selected from the group consisting of vanadium, manganese, molybdenum, tungsten, niobium and tantalum, "a" ranges from about 40 to 85 atom percent, "b" ranges from 0 to about 45 atom percent, "c" and "d" each range from 0 to about 20 atom percent and "e" ranges from about 15 to 25 atom percent, with the proviso that "b", "c" and "d" cannot all be zero simultaneously.
 2. The amorphous metal alloy of claim 1 in which "e" ranges from about 17 to 22 atom percent.
 3. The amorphous metal alloy of claim 1 in which "c" ranges from about 4 to 16 atom percent.
 4. The amorphous metal alloy of claim 1 in which M" is molybdenum and "d" ranges from about 0.4 to 8 atom percent.
 5. The amorphous metal alloy of claim 4 in which "d" ranges from about 0.4 to 0.8 atom percent.
 6. The amorphous metal alloy of claim 4 in which "d" ranges from about 4 to 8 atom percent.
 7. The amorphous metal alloy of claim 1 consisting essentially of the composition

    Fe.sub.50-70 (Ni,Co).sub.5-15 Cr.sub.5-16 Mo.sub.0-8 B.sub.16-22.


8. The amorphous metal alloy of claim 1 consisting essentially of the composition

    Fe.sub.60-67 Ni.sub.3-7 Co.sub.3-7 Cr.sub.7-10 Mo.sub.0.4-0.8 B.sub.17-20.


9. The amorphous metal alloy of claim 1 consisting essentially of the composition

    Ni.sub.40-50 Fe.sub.4-10 Co.sub.5-25 Cr.sub.8-12 Mo.sub.0-9 B.sub.15-22.


10. 10. the amorphous metal alloy of claim 1 consisting essentially of the composition

    Co.sub.40-50 Fe.sub.5-20 Ni.sub.0-20 Cr.sub.4-15 Mo.sub.0-9 B.sub.15-23.


11. The amorphous metal alloy of claim 1 in which "c" and "d" are both zero.
 12. The amorphous metal alloy of claim 9 consisting essentially of the composition Ni₄₅ Fe₅ Co₂₀ Cr₁₀ Mo₄ B₁₆.
 13. The amorphous metal alloy of claim 10 consisting essentially of the composition Fe₇₀ Co₁₀ B₂₀. 